SEM and Site Usability
Usability and search friendliness go hand in hand. If products and services are easy to find, and the Web site easy to use (resulting in higher conversions), the site should easily maintain high-quality search engine traffic. Yet many search engine marketing (SEM) firms offering search-engine-friendly design don't have staff trained, certified, or experienced in Web site usability.
The link address is: http://www.clickz.com/experts/search/results/article.php/3482316